Anyone with functioning kidneys is fine. Anyone with kidney problems probably isn’t drinking much soda anyway, and if they are that’s their choice. The occasional diet soda won’t kill you any faster than, say, standing outside would.
Nobody’s drinking 5 LITERS of soda in a day. If they are? More power to ‘em.
This isn’t a big deal in the slightest. A lot of diet sodas aren’t even using aspartame anymore, so it’s nearly a moot point.